A broadband wireless access system is a next generation communication system for supporting mobility for a local area data communication method using a fixed access point. Various standards have been proposed for the broadband wireless access system, and the IEEE 802.16 group have actively progressed international standardization of the broadband wireless access system.
The conventional wireless LAN (Local Area Network) method allows local area wireless communication with reference to the fixed access point, which however supports local area data communication through a wireless method and does not guarantee mobility of the mobile station.
The broadband wireless access method such as the IEEE 802.16 guarantees the mobility to provide a seamless data communication service when a mobile station moves from a cell covered by a base station to another cell covered by another base station.
The method for estimating the mobile station's position in the mobile communication system includes a method for attaching a position estimation device to the mobile station, a method for the mobile station to generate a predetermined signal, a method for the mobile station and the base station to use a separately allocated channel, and a method for using three angle positioning of the base station.
The method for attaching a position estimation device to the mobile station uses a global positioning system (GPS) and transmits information acquired through the GPS to the base station to estimate the position of the mobile station. The method for the mobile station to generate a predetermined signal is a method for the base station or a repeater to receive a predetermined signal from the mobile station and estimate the position. The method for the mobile station and the base station to use a separately allocated channel is a method for estimating the position by exchanging position information through a predetermined channel. The method for using the three angle positioning of the base station is a method for at least three base stations to measure a frequency radiated by a predetermined mobile station and estimate the position of the mobile station by using a three angle positioning scheme.
However, the above-noted position estimation methods of the mobile station are disadvantageous in terms of cost, efficiency, and utilization of frequencies because they attach an additional device to the mobile station or control the mobile station to perform additional functions. Also, it is difficult to use the three angle positioning method of the existing mobile communication when all the base stations use the same frequency.
It is possible to estimate the position of the mobile station by using the difference of signal arrival times between the mobile station and many base stations, and the difference of the signal arrival times is measured through a ranging process that is a basic function of the mobile station. However, the ranging method is a contention-based access method in which a collision occurs when a plurality of mobile stations simultaneously attempt the ranging process, and thereby it is difficult to measure the arrival time of the signal that is transmitted by the corresponding mobile station.
Further, the ranging process in the broadband radio access system such as the IEEE 802.16 is performed through the code division multiple access (CDMA) codes, and in this instance, it is difficult to identify the mobile station having transmitted the corresponding CDMA code since the CDMA code includes no user information, and hence it is difficult to measure the position of the mobile station.